Stimulatory effect of serum on 86Rb washout from vascular smooth muscle cells in culture.
In order to elucidate the effect of serum on passive K permeability of vascular smooth muscle cells (VSMC) membrane, outward passive K permeability yielded as washout rate constant (Kc) of 86Rb washout, was measured in the presence and in the absence of cation transport modulators using VSMC in culture. The overall Kc of 86Rb washout subjected to 1% serum was significantly larger than that in controls. This stimulated Kc was substantially blunted in the presence of 10(-4) M amiloride and was partially inhibited with 5 x 10(-4) M bumetanide. Angiotensin II of 10(-5) M exerted to a lesser extent, a similar significant stimulatory effect on Kc of 86Rb washout, which effect was inhibited with application of amiloride. Additionally, Ca-antagonist, 10(-5) M nifedipine reduced serum-stimulated Kc to the basal level. It is concluded that both serum and angiotensin II increase K permeability in cultured VSMC. A part of this effect of serum may be attributable to angiotensin II in the serum. Furthermore, it is suggested that the stimulatory effect of serum on membrane permeability may be exerted, at least in part, via activation of both Na-H antiport and Na-K co-transport, possibly through mechanisms in conjunction with intracellular Ca.
Nakamura
K
K
Second Department of Internal Medicine, Jikei University School of Medicine, Tokyo, Japan.
Kuriyama
S
S
Tomonari
H
H
Kaguchi
Y
Y
Hashimoto
T
T
Sakai
O
O
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001790:Blood Physiological Phenomena; D002034:Bumetanide / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D012414:Rubidium Radioisotopes; D012964:Sodium / Q000378:metabolism
D012414:Rubidium Radioisotopes; D002034:Bumetanide; D000804:Angiotensin II; D012964:Sodium; D009543:Nifedipine; D011188:Potassium